isDirectMapping

public boolean isDirectMapping ()

Returns true if the ParallaxTarget is directly mapping from source value,
directUpdate(Number) will be used to update value, otherwise update(fraction) will
be called to update value. Default implementation returns false.

update

public void update (float fraction)

Implementation class is supposed to update target with the provided fraction
(between 0 and 1). The fraction represents percentage of completed change (e.g. scroll) on
target. Called only when isDirectMapping() is false.